IEEE 802.15 describes a communication architecture, which may enable communicating devices (DEVs) to communicate via wireless personal area networks (WPANs). Many DEVs utilized in WPANs are small or handheld devices, such as personal digital assistants, portable computers, or consumer electronics devices such as digital video recorders or set top boxes. IEEE 802.15 is a short-range wireless communications standard that enables connection between consumer and computer equipment while eliminating wires. IEEE 802.15 WPAN DEVs may utilize frequencies in the 57 GHz to 66 GHz range for communication.
A plurality of communicating DEVs in a WPAN environment may comprise a network known as a piconet. One of the DEVs in a piconet may function as a piconet coordinator (or controller), or PNC. The PNC may provide overall coordination for the communication between DEVs in a piconet. The piconet may comprise the PNC and DEVs, which are associated with the PNC.
The DEVs may communicate through the transmission and/or reception of protocol data units (PDU) referred to as frames. A frame may correspond to a PDU that is associated with a physical (PHY) layer protocol in a protocol reference model (PRM). The frame may comprise a physical layer convergence procedure (PLCP) preamble field, a PLCP header field and a physical layer service data unit (PSDU) field. The PLCP preamble field is utilized by a receiver of the PDU to detect a potentially receivable signal and to establish frequency and/or timing synchronization with the received PDU. The PLCP header field is utilized by a receiver of the PDU to determine the length of the PSDU field, typically measured in octets, and to determine a data rate for data contained within the PSDU field. The PSDU field may be referred to as a payload field. The payload field may comprise data that are being communicated from a source DEV to a destination DEV.
Radio frequency (RF) communications between communicating devices via the wireless communication medium within the 60 GHz frequency range are typically directional in nature. Thus transmitting DEVs may transmit RF signal energy from a given antenna in a given direction while not transmitting RF signal energy in other directions from the given antenna. Thus, given two potential recipient DEVs located at, for example, equal distances in opposite physical directions relative to a transmitting DEV, a potential recipient DEV which is in the direction of RF signal energy transmission may receive signals from the transmitting DEV while the other potential recipient DEV may not.
Prior to attempting to transmit signals via the wireless communication medium, a communicating DEV, which utilize the CSMA/CA protocol, typically attempts to determine whether there are any DEVs that are transmitting signals via the wireless communication medium. This determination is referred to as a clear channel assessment (CCA). When the CCA indicates that there are no other DEVs, which are transmitting signals, the communicating DEV may determine that the wireless communication medium is available for transmission of signals. The communicating DEV may attempt to reserve the wireless communication medium for signal transmission for a given time duration by transmitting a request to send (RTS) frame. The RTS frame may identify the communicating DEV as a source DEV and may also identify one or more destination DEVs. In response, one or more destination DEVs identified in the RTS frame may send a clear to send (CTS) frame to the source DEV. After completing the RTS/CTS frame exchange, the source DEV and destination DEV(s) may communicate by sending frames via the wireless communication medium.
Because of the directional nature of 60 GHz signal transmission, the effectiveness of CSMA/CA protocol in achieving collision avoidance may be impaired due to capture effect and/or deafness. Deafness is a phenomenon, which is observed at a transmitting DEV, in which a plurality of transmitting DEVs concurrently transmit signals via the wireless communication medium, wherein because of the directional nature of each transmitting signal, each transmitting DEV may not detect the signals being transmitted by the other transmitting DEVs. In other words, because of the inability to detect the energy from signals transmitted by other transmitting DEVs, the CCA performed at each transmitting DEV may indicate that the wireless communication medium is available for signal transmission.
Capture effect is a phenomenon, which is observed at a receiving DEV. Because the various transmitted signals may be received at the respective destination DEVs with differing signal-to-interference plus noise ratios (SINR), PDUs received via signals with higher SINR values may be successfully received at the corresponding destination DEV(s) while PDUs received via signals with lower SINR values may not be successfully received at the corresponding destination DEV(s).
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.